Rechargeable battery temperature detection method, power management device and electronic system

ABSTRACT

A rechargeable battery temperature detection method adapted to an electronic system includes detecting a status of a processor of the electronic system when an external power is input to a power conversion module of the electronic system; determining whether a thermistor of the electronic system is conducted to a fuel gauge or a charge control circuit according to the state of the processor such that the fuel gauge or the charge control circuit determine a temperature sensing result via the thermistor. The thermistor is disposed adjacent to a rechargeable battery and has a resistance which varies with a temperature of the rechargeable battery. The temperature sensing result is related to the resistance.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a rechargeable battery temperaturedetection method, a power management device and an electronic system,and more particularly, to a rechargeable battery temperature detectionmethod, a power management device and an electronic system that canswitch circuits according to states of a processor in order to preventtemperature of a rechargeable battery from being out of control.

2. Description of the Prior Art

Along with the ever-increasing popularity of portable electronicdevices, demand for a rechargeable battery has grown dramatically inrecent years. When recharging a rechargeable battery, however, theelectric current passing through will release heat (known as jouleheating), which causes the rechargeable battery to become hot. If therechargeable battery becomes too hot, it may experience thermal runaway,become damaged, or even explode. To ensure charging safety, a thermistormay be disposed in the portable electronic device in proximity to therechargeable battery and adapted for a fuel gauge to detect temperatureof the rechargeable battery. The fuel gauge determines the temperatureof the rechargeable battery according to the resistance of thethermistor, and sends a temperature sensing result to the processor. Theprocessor then transmits the temperature sensing result to the chargingcontrol circuit, which can control a magnitude of a charging currentflowing from a charging circuit to the rechargeable battery to preventthermal runaway.

The temperature sensing results detected by the fuel gauge must beceaselessly transmitted to the charging control circuit through theprocessor. If the processor crashes, the charging control circuit cannotadjust the charging current according to the temperature sensing result,and charging safety will be put at risk. Moreover, in order to ensurethat the charging control circuit can accurately determine thetemperature of the rechargeable battery even when the portableelectronic device is in a sleeping or a shutdown state, the processormust consume certain amounts of electricity to transmit the temperaturesensing result to the charging control circuit. Accordingly, ensuringcharging safety and saving power even when the processor is executed indifferent states is a main objective in the field.

SUMMARY OF THE INVENTION

Therefore, it is one of the objectives of the disclosure to provide arechargeable battery temperature detection method, a power managementdevice and an electronic system, which can switch circuits according tostates of a processor, thereby preventing temperature of a rechargeablebattery from being out of control whether the processor is operated in aworking state or not.

An embodiment of the invention provides a rechargeable batterytemperature detection method adapted to an electronic system. Therechargeable battery temperature detection method comprises detecting astate of a processor of the electronic system when an external power isinput to a power conversion module of the electronic system; anddetermining whether electric currents are conducted between a thermistorof the electronic system and a fuel gauge or between the thermistor anda charging control circuit according to the state of the processor,wherein the fuel gauge or the charging control circuit determines atemperature sensing result via the thermistor; wherein the thermistor isdisposed adjacent to a rechargeable battery and has a resistance whichvaries with a temperature of the rechargeable battery, and thetemperature sensing result is related to the resistance.

An embodiment of the invention provides a power management deviceadapted to an electronic system. The power management device comprises athermistor, disposed adjacent to a rechargeable battery of theelectronic system and having a resistance which varies with atemperature of the rechargeable battery; a fuel gauge, configured tocalculate a charge storage capacity of the rechargeable battery anddetermine a temperature sensing result according to the resistance ofthe thermistor; a charging control circuit, configured to control how acharging circuit charges the rechargeable battery and determine thetemperature sensing result according to the resistance of thethermistor; and a switch module, coupled between the thermistor, thefuel gauge and the charging control circuit and configured to conductelectric currents between the thermistor and a fuel gauge or between thethermistor and a charging control circuit according to a state of aprocessor of the electronic system, wherein the fuel gauge or thecharging control circuit determines the temperature sensing result viathe thermistor.

An embodiment of the invention provides an electronic system. Theelectronic system comprises a power conversion module, configured tooutput a direct current (DC) voltage; a processor; a rechargeablebattery; a charging circuit, configured to receive the DC voltage fromthe power conversion module and provide a charging current for therechargeable battery; and a power management device. The powermanagement device comprises a thermistor, disposed adjacent to therechargeable battery and having a resistance which varies with atemperature of the rechargeable battery; a fuel gauge, configured tocalculate a charge storage capacity of the rechargeable battery anddetermine a temperature sensing result according to the resistance ofthe thermistor; a charging control circuit, configured to control howthe charging circuit charges the rechargeable battery and determine thetemperature sensing result according to the resistance of thethermistor; and a switch module, coupled between the processor, thethermistor, the fuel gauge and the charging control circuit andconfigured to conduct electric currents between the thermistor and afuel gauge or between the thermistor and a charging control circuitaccording to a state of the processor, wherein the fuel gauge or thecharging control circuit determines the temperature sensing result viathe thermistor.

These and other objectives of the present invention will no doubt becomeobvious to those of ordinary skill in the art after reading thefollowing detailed description of the preferred embodiment that isillustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram illustrating an electronic systemaccording to an embodiment of the invention.

FIG. 2 illustrates a rechargeable battery temperature detection processaccording to an embodiment of the invention.

FIG. 3 is a schematic diagram illustrating a switch module according toan embodiment of the invention.

FIG. 4 is a schematic diagram illustrating a charging control circuitaccording to an embodiment of the invention.

FIG. 5 is a schematic diagram illustrating a fuel gauge according to anembodiment of the invention.

DETAILED DESCRIPTION

Please refer to FIG. 1, which is a schematic diagram illustrating anelectronic system 10 according to an embodiment of the invention. Theelectronic system 10 may be a portable electronic device or anyelectronic system with an independent power supply system such as alaptop, a smart phone, or a tablet. The electronic system 10 comprises apower conversion module 102, a processor 104, a rechargeable battery106, a charging circuit 108 and a power management device 110. The powermanagement device 110 comprises a thermistor 112, a fuel gauge 114, acharging control circuit 116 and a switch module 118. The thermistor 112is disposed adjacent to the rechargeable battery 106, and resistance ofthe thermistor 112 can vary with temperature of the rechargeable battery106. The fuel gauge 114 is utilized to calculate charge storage capacityof the rechargeable battery 106 and measure the resistance of thethermistor 112 so as to provide the charge storage capacity of therechargeable battery 106 and temperature information for the processor104. The power conversion module 102 can convert an external powerExt_Power (for example, an alternating current (AC) power) into a directcurrent (DC) power DC_Power and then provide the direct current powerDC_Power to the charging circuit 108. The charging control circuit 116can control the charging circuit 108 to convert the direct current powerDC_Power into a proper charging current according to the temperature ofthe rechargeable battery 106, in order to charge the rechargeablebattery 106. The switch module 118 is coupled between the thermistor112, the fuel gauge 114 and the charging control circuit 116. The switchmodule 118 can detect state signals STATE_(—)1, STATE_(—)2 of theprocessor 104 by means of a pin on the processor 104; the switch module118 can alternately conduct electric current between the thermistor 112and the fuel gauge 114 or between the thermistor 112 and the chargingcontrol circuit 116 according to a state of the processor 104.Consequently, either the fuel gauge 114 or the charging control circuit116 can determine the temperature sensing result RST_(—)1 or RST_(—)2according to the resistance of the thermistor 112, wherein thetemperature sensing results RST_(—)1 and RST_(—)2 relate to thetemperature of the rechargeable battery 106.

More specifically, when an external power Ext_Power is input to thepower conversion module 102—for example, a charger is plugged into thepower conversion module 102 or a socket of the power conversion module102—the switch module 118 conducts electric current between thethermistor 112 and the fuel gauge 114 when the switch module 118 detectsthe state signal STATE_(—)1 from the processor 104 and determines thatthe processor 104 is operated in a working state. The fuel gauge 114 canthereby determine the temperature sensing result RST_(—)1 according tothe resistance of the thermistor 112. The fuel gauge 114 then sends thetemperature sensing result RST_(—)1 to the processor 104, and theprocessor 104 further transmits the temperature sensing result RST_(—)1to the charging control circuit 116, such that the charging controlcircuit 116 can control how the charging circuit 108 charges therechargeable battery 106.

When the external power Ext_Power is input to the power conversionmodule 102, the switch module 118 conducts electric current between thethermistor 112 and the charging control circuit 116 when the switchmodule 118 detects the state signal STATE_(—)2 from the processor 104and determines that the processor 104 is not operated in a workingstate. The charging control circuit 116 can thereby determine thetemperature sensing result RST_(—)2 according to the resistance of thethermistor 112 and accordingly control how the charging circuit 108charges the rechargeable battery 106. Therefore, when the electronicsystem 10 crashes, because the charging control circuit 116 is coupledto the thermistor 112, the charging control circuit 116 can still obtainthe temperature sensing result RST_(—)2 and accordingly control thecharging circuit 108, thereby assuring charging safety. In addition,when the electronic system 10 is operated in a sleeping or a shutdownstate, because the charging control circuit 116 is coupled to thethermistor 112, the processor 104 does not need to transmit thetemperature sensing result from the fuel gauge 114 to the chargingcontrol circuit 116, thereby saving power.

Via the switch module 118 coupled between the thermistor 112, the fuelgauge 114 and the charging control circuit 116, the power managementdevice 110 can simultaneously assure charging safety and save energy. Arelated operation method can be summarized into a rechargeable batterytemperature detection process 20 as shown in FIG. 2. The rechargeablebattery temperature detection process 20 includes the following steps:

Step S200: start.

Step S202: when the external power Ext_Power is input to the powerconversion module 102, the switch module 118 detects whether theprocessor 104 is operated in a working state. If yes, go to Step 204;otherwise, go to Step 210.

Step S204: the switch module 118 conducts electric current between thethermistor 112 and the fuel gauge 114, and the fuel gauge 114 determinesthe temperature sensing result RST_(—)1 according to the resistance ofthe thermistor 112.

Step S206: the fuel gauge 114 outputs the temperature sensing resultRST_(—)1 to the processor 104.

Step S208: the processor 104 outputs the temperature sensing resultRST_(—)1 to the charging control circuit 116.

Step S210: the switch module 118 conducts electric current between thethermistor 112 and the charging control circuit 116, and the chargingcontrol circuit 116 determines the temperature sensing result RST_(—)2according to the resistance of the thermistor 112.

Step S212: the charging control circuit 116 controls how the chargingcircuit 108 charges the rechargeable battery 106 to appropriately adjustcharging currents flowing into the rechargeable battery 106.

The rechargeable battery temperature detection process 20 is anoperation method of the power management device 110 by which the switchmodule 118 can alternately conduct electric current between thethermistor 112 and the fuel gauge 114 or between the thermistor 112 andthe charging control circuit 116 corresponding to different states ofthe processor 104. When the processor 104 is operated in a workingstate, the switch module 118 conducts electric current between thethermistor 112 and the fuel gauge 114, such that the fuel gauge 114 candetermine the temperature sensing result RST_(—)1 according to theresistance of the thermistor 112. The fuel gauge 114 sends a measuredcharge storage capacity of the rechargeable battery 106 and thetemperature sensing result RST_(—)1 to the processor 104, and theprocessor 104 further transmits the temperature sensing result RST_(—)1to the charging control circuit 116. Therefore, the charging controlcircuit 116 can control how the charging circuit 108 charges therechargeable battery 106. When the processor 104 is not operated in aworking state, the switch module 118 conducts electric current betweenthe thermistor 112 and the charging control circuit 116, such that thecharging control circuit 116 can determine the temperature sensingresult RST_(—)2 according to the resistance of the thermistor 112 andaccordingly control how the charging circuit 108 charges therechargeable battery 106. Please note that voltages of the temperaturesensing results RST_(—)1 and RST_(—)2 may be the same; nevertheless, thepresent invention is not limited thereto and the voltages of thetemperature sensing results RST_(—)1 and RST_(—)2 may differ accordingto system requirements or design considerations. Furthermore, when thetemperature sensing results RST_(—)1 and RST_(—)2 indicate that thetemperature of the rechargeable battery 106 is too high or too low, thecharging control circuit 116 may force the charging circuit 108 toreduce the charging current flowing to the rechargeable battery 106 oreven to stop charging the rechargeable battery 106 to ensure chargingsafety.

Please note that the electronic system 10 in FIG. 1 or the rechargeablebattery temperature detection process 20 in FIG. 2 are embodiments ofthe invention; however, the present invention is not limited thereto,and those skilled in the art might make modifications or alterationsaccordingly. For example, the switch module 118 detects the statesignals STATE_(—)1, STATE_(—)2 of the processor 104 via a pin of theprocessor 104 so as to determine whether the processor 104 is operatedin a working state. The state signals STATE_(—)1 and STATE_(—)2 may bedifferent voltage levels provided on one pin of the processor 104; forexample, the state signals STATE_(—)1 and STATE_(—)2 may respectively bea high voltage level and a low voltage level. In the electronic system10, the thermistor 106 may be a negative temperature coefficient (NTC)thermistor or a positive temperature coefficient (PTC) thermistor, butis not limited herein; any component where the resistance varies withtemperature can serve as a thermistor. Moreover, since the externalpower Ext_Power can be an AC power or a DC power, the power conversionmodule 102 can be an AC-to-DC converter or a DC-to-DC converter in orderto covert the external power Ext_Power into a proper DC power DC_Power,but is not limited thereto. The rechargeable battery 106 can be alithium-ion battery, a Nickel-cadmium (NiCd) battery, aNickel-metalhydride (NiMH) battery, etc., but is not limited herein; therechargeable battery 106 can also be any other rechargeable battery. Theprocessor 104 can be a microcontroller, a digital signal processor(DSP), a field-programmable gate array (FPGA), a complex programmablelogic device (CPLD), an application specific integrated circuit (ASIC)or a central processor unit (CPU), but is not limited thereto. Theelectronic system 10 can be various electronic devices such as a smartphone, a personal digital assistant (PDA) or a laptop, but is notlimited thereto.

The switch module 118 is utilized to switch electrical connections froma connection between the thermistor 112 and the fuel gauge 114 to aconnection between the thermistor 112 and the charging control circuit116, and vice versa, but may be implemented in any other approach orstructure. For example, the switch module 118 may be a double-poledouble-throw (DPDT) digital switch or a dual single-pole double-throw(SPDT) digital switch and may be further modified according to differentsystem requirements or design considerations. Please refer to FIG. 3,which is a schematic diagram illustrating the switch module 118according to an embodiment of the invention. The switch module 118comprises single-pole double-throw switches 318 a and 318 b, anddifferent numerals denote different pins. Specifically, a pin 11 of thesingle-pole double-throw switch 318 a is electrically connected to thethermistor 112. Pins 2 and 9 are electrically connected to the fuelgauge 114 and the charging control circuit 116, respectively. Electriccurrents are conducted between the thermistor 112 and the fuel gauge 114when a pin 1 detects the state signal STATE_(—)1 from the processor 104.Alternatively, electric currents are conducted between the thermistor112 and the charging control circuit 116 when the pin 1 detects thestate signal STATE_(—)2 from the processor 104. When a pin 5 of thesingle-pole double-throw switch 318 b detects the state signalsSTATE_(—)1 and STATE_(—)2, the charging control circuit 116 electricallyconnected to pin 4 and the fuel gauge 114 electrically connected to pin7 are grounded through a resistor 320 electrically connected to a pin 6.The resistor 320 may be omitted according to different systemrequirements and the pin 6 is thus grounded directly.

The charging control circuit 116 is utilized to determine thetemperature sensing result RST_(—)2 according to the resistance of thethermistor 112, but may be implemented in any other approach orstructure. For example, please refer to FIG. 4, which is a schematicdiagram illustrating the charging control circuit 116 according to anembodiment of the invention. The charging control circuit 116 comprisespower sources 420 a, 420 b, resistors R, R_(—)1-R_(—)4, comparators 430a-430 c and a calculating unit 440. The resistors R_(—)1-R_(—)4 areconnected in series between the power source 420 a of voltage value VDD1and a grounding terminal and respectively have resistances r1, r2, r3and r4. The resistors R_(—)1-R_(—)4, which serve as a voltage divider,can provide voltage values

${{\frac{{r\; 2} + {r\; 3} + {r\; 4}}{{r\; 1} + {r\; 2} + {r\; 3} + {r\; 4}} \cdot {VDD}}\; 1},{{\frac{{r\; 3} + {r\; 4}}{{r\; 1} + {r\; 2} + {r\; 3} + {r\; 4}} \cdot {VDD}}\; 1},{{\frac{r\; 4}{{r\; 1} + {r\; 2} + {r\; 3} + {r\; 4}} \cdot {VDD}}\; 1}$

for positive input terminals of the comparators 430 a-430 c,respectively. When the switch module 118 conducts electric currentbetween the thermistor 112 and the charging control circuit 116, theresistor R and the thermistor 112 of a negative temperature coefficientare connected in series between the power source 420 b of voltage valueVDD2 and a grounding terminal, and respectively have resistances r andr112. The resistor R and the thermistor 112, which serve as anothervoltage divider, can provide voltage value

${\frac{r\; 112}{r + {r\; 112}} \cdot {VDD}}\; 2$

for negative input terminals of the comparators 430 a-430 c.

The comparators 430 a-430 c send results to the calculating unit 440,and the calculating unit 440 transmits the calculated temperaturesensing result RST_(—)2 to the charging circuit 108. The voltage ratioof the resistors R_(—)1-R_(—)4 can be adjusted according to varioussystem requirements; for example, values

${{\frac{{r\; 2} + {r\; 3} + {r\; 4}}{{r\; 1} + {r\; 2} + {r\; 3} + {r\; 4}} \cdot {VDD}}\; 1},{{\frac{{r\; 3} + {r\; 4}}{{r\; 1} + {r\; 2} + {r\; 3} + {r\; 4}} \cdot {VDD}}\; 1},{{\frac{r\; 4}{{r\; 1} + {r\; 2} + {r\; 3} + {r\; 4}} \cdot {VDD}}\; 1}$

may be in a ratio of 73.5:47.2:44.7. As a result, if

${\frac{r\; 112}{r + {r\; 112}} \cdot {VDD}}\; 2$

is less than

${{\frac{r\; 4}{{r\; 1} + {r\; 2} + {r\; 3} + {r\; 4}} \cdot {VDD}}\; 1},$

this means that the temperature of the rechargeable battery 106 is toohigh and the charging circuit 108 should reduce the charging currentflowing into the rechargeable battery 106 immediately, or even stopcharging the rechargeable battery 106, to ensure charging safety. If

${\frac{r\; 112}{r + {r\; 112}} \cdot {VDD}}\; 2$

is within a range of

${\frac{r\; 4}{{r\; 1} + {r\; 2} + {r\; 3} + {r\; 4}} \cdot {VDD}}\; 1$

to

${{\frac{{r\; 3} + {r\; 4}}{{r\; 1} + {r\; 2} + {r\; 3} + {r\; 4}} \cdot {VDD}}\; 1},$

this means that the temperature of the rechargeable battery 106 is quitehigh and an alert signal may be output. If

${\frac{r\; 112}{r + {r\; 112}} \cdot {VDD}}\; 2$

is within a range of

${{\frac{{r\; 3} + {r\; 4}}{{r\; 1} + {r\; 2} + {r\; 3} + {r\; 4}} \cdot {VDD}}\; 1},$

to

${{\frac{{r\; 2} + {r\; 3} + {r\; 4}}{{r\; 1} + {r\; 2} + {r\; 3} + {r\; 4}} \cdot {VDD}}\; 1},$

this means that the temperature of the rechargeable battery 106 isnormal. In this case, the rechargeable battery 106 will still becharged, and the charging current may even increase. If

${\frac{r\; 112}{r + {r\; 112}} \cdot {VDD}}\; 2$

is greater than

${{\frac{{r\; 2} + {r\; 3} + {r\; 4}}{{r\; 1} + {r\; 2} + {r\; 3} + {r\; 4}} \cdot {VDD}}\; 1},$

this means that the temperature of the rechargeable battery 106 is low,in which case the charging circuit 108 can reduce the charging currentflowing into the rechargeable battery 106 or even stop charging therechargeable battery 106. Therefore, based on the relation between theresistance of the thermistor 112 and the temperature of the rechargeablebattery 106, those skilled in the art may adjust the ratio of theresistances of the resistors R, R_(—)1-R_(—)4 so that the chargingcontrol circuit 116 can accurately control the charging method of thecharging circuit 108.

The fuel gauge 114 is utilized to determine the temperature sensingresult RST_(—)1 according to the resistance of the thermistor 112, butmay be implemented in any other approach or structure. For example,please refer to FIG. 5, which is a schematic diagram illustrating thefuel gauge 114 according to an embodiment of the invention. The fuelgauge 114 comprises power sources 520 a, 520 b, resistors R′, R_(—)1′, acomparator 530 and a calculating unit 540. The power source 420 a canprovide a voltage value VDD1′ to a positive input terminal of thecomparator 530. When the switch module 118 conducts electric currentbetween the thermistor 112 and the fuel gauge 114, the resistor R′ andthe thermistor 112 are connected in series between the power source 520b of voltage value VDD2′ and a grounding terminal, and respectively haveresistances r′ and r112. The resistor R′ and the thermistor 112, whichserves as another voltage divider, can provide a voltage value

${\frac{r\; 112}{r^{\prime} + {r\; 112}} \cdot {VDD}}\; 2$

to a negative input terminal of the comparator 530. The comparator 530sends results to the calculating unit 540, and the calculating unit 540transmits the calculated temperature sensing result RST_(—)1 to theprocessor 104. The temperature sensing result RST_(—)1 and thetemperature of the rechargeable battery 106 can then be determinedaccording to the resistance of the thermistor 112.

FIGS. 3 to 5 are, respectively, embodiments of the switch module 118,the charging control circuit 116 and the fuel gauge 114 in the powermanagement device 110; however, the present invention is not limited tothe illustrated embodiments. Those skilled in the art may adjust theimplementation of the power management device 110 according to systemrequirements to alternatively connect the thermistor 112 to the fuelgauge 114 or the charging control circuit 116 so as to ensure chargingsafety and save power.

In the prior art, temperature sensing results detected by a fuel gaugemust be ceaselessly transmitted to a charging control circuit through aprocessor. As a result, when the processor cannot be executed normally,charging safety will be put at risk. In contrast, even when theprocessor 104 of the present invention does not operate normally or evenwhen the electronic system 10 is operated in a sleeping or a shutdownstate, because the switch module 118 conducts electric currents betweenthe thermistor 112 and the charging control circuit 116, the chargingcontrol circuit 116 can still obtain the temperature sensing resultRST_(—)2 and accordingly control the charging circuit 108 toappropriately adjust the charging current, thereby assuring chargingsafety and saving power.

To sum up, electric currents are conducted between the thermistor andthe charging control circuit or between the thermistor and the fuelgauge according to states of the processor, thereby assuring chargingsafety and saving power.

Those skilled in the art will readily observe that numerousmodifications and alterations of the device and method may be made whileretaining the teachings of the invention. Accordingly, the abovedisclosure should be construed as limited only by the metes and boundsof the appended claims.

What is claimed is:
 1. A rechargeable battery temperature detectionmethod, adapted to an electronic system, comprising: detecting a stateof a processor of the electronic system when an external power is inputto a power conversion module of the electronic system; and determiningwhether electric currents are conducted between a thermistor of theelectronic system and a fuel gauge or between the thermistor and acharging control circuit according to the state of the processor,wherein the fuel gauge or the charging control circuit determines atemperature sensing result via the thermistor; wherein the thermistor isdisposed adjacent to a rechargeable battery and has a resistance whichvaries with a temperature of the rechargeable battery, and thetemperature sensing result is related to the resistance.
 2. Therechargeable battery temperature detection method according to claim 1,wherein the step of determining whether electric currents are conductedbetween the thermistor of the electronic system and the fuel gauge orbetween the thermistor and the charging control circuit according to thestate of the processor comprises: conducting electric currents betweenthe thermistor and the fuel gauge when the processor is operated in aworking state, wherein the fuel gauge determines the temperature of therechargeable battery according to the resistance of the thermistor andthereby determines the temperature sensing result.
 3. The rechargeablebattery temperature detection method according to claim 2, furthercomprising: utilizing the fuel gauge to transmit the temperature sensingresult to the processor, wherein the processor controls how a chargingcircuit charges the rechargeable battery according to the temperaturesensing result.
 4. The rechargeable battery temperature detection methodaccording to claim 1, wherein the step of determining whether electriccurrents are conducted between the thermistor of the electronic systemand the fuel gauge or between the thermistor and the charging controlcircuit according to the state of the processor comprises: conductingelectric currents between the thermistor and the charging controlcircuit when the processor is not operated in a working state, whereinthe charging control circuit determines the temperature of therechargeable battery according to the resistance of the thermistor andthereby determines the temperature sensing result.
 5. The rechargeablebattery temperature detection method according to claim 4, furthercomprising: utilizing the charging control circuit to adjust how acharging circuit charges the rechargeable battery according to thetemperature sensing result.
 6. The rechargeable battery temperaturedetection method according to claim 4, wherein when the electronicsystem is operated in a state selected from a sleeping state, a shutdownstate and a crashed state, the processor is not operated in the workingstate.
 7. The rechargeable battery temperature detection methodaccording to claim 1, wherein the thermistor is a negative temperaturecoefficient (NTC) thermistor or a positive temperature coefficient (PTC)thermistor.
 8. A power management device, adapted to an electronicsystem, comprising: a thermistor, disposed adjacent to a rechargeablebattery of the electronic system and having a resistance which varieswith a temperature of the rechargeable battery; a fuel gauge, configuredto calculate a charge storage capacity of the rechargeable battery anddetermine a temperature sensing result according to the resistance ofthe thermistor; a charging control circuit, configured to control how acharging circuit charges the rechargeable battery and determine thetemperature sensing result according to the resistance of thethermistor; and a switch module, coupled between the thermistor, thefuel gauge and the charging control circuit and configured to conductelectric currents between the thermistor and a fuel gauge or between thethermistor and a charging control circuit according to a state of aprocessor of the electronic system, wherein the fuel gauge or thecharging control circuit determines the temperature sensing result viathe thermistor.
 9. The power management device according to claim 8,wherein when the processor is operated in a working state, the switchmodule conducts electric currents between the thermistor and the fuelgauge, wherein the fuel gauge determines the temperature of therechargeable battery according to the resistance of the thermistor andthereby determines the temperature sensing result.
 10. The powermanagement device according to claim 9, wherein the fuel gauge isfurther configured to transmit the temperature sensing result to theprocessor, wherein the processor controls how the charging circuitcharges the rechargeable battery according to the temperature sensingresult.
 11. The power management device according to claim 8, whereinwhen the processor is not operated in a working state, the switch moduleconducts electric currents between the thermistor and the chargingcontrol circuit, wherein the charging control circuit determines thetemperature of the rechargeable battery according to the resistance ofthe thermistor and thereby determines the temperature sensing result.12. The power management device according to claim 11, wherein thecharging control circuit is further configured to adjust how thecharging circuit charges the rechargeable battery according to thetemperature sensing result.
 13. The power management device according toclaim 11, wherein when the electronic system is operated in a stateselected from a sleeping state, a shutdown state and a crashed state,the processor is not operated in the working state.
 14. The powermanagement device according to claim 8, wherein the switch module isfurther configured to determine the state of the processor according toa state signal of the processor.
 15. The power management deviceaccording to claim 8, wherein the charging control circuit comprises: afirst resistor, electrically connected between the charging circuit anda first voltage source; a serial resistor, electrically connectedbetween a second voltage source and a grounding terminal and comprisinga plurality of resistors connected in series, wherein resistances of theplurality of resistors respectively relates to the resistance of thethermistor; and a plurality of comparators, wherein each comparator ofthe plurality of comparator comprises a positive input terminalelectrically connected between two adjacent resistors of the pluralityof resistors, a negative input terminal coupled between the switchmodule and the first resistor, and an output terminal coupled to thecharging circuit.
 16. The power management device according to claim 8,wherein the thermistor is a negative temperature coefficient (NTC)thermistor or a positive temperature coefficient (PTC) thermistor. 17.An electronic system, comprising: a power conversion module, configuredto output a direct current (DC) voltage; a processor; a rechargeablebattery; a charging circuit, configured to receive the DC voltage fromthe power conversion module and provide a charging current for therechargeable battery; and a power management device, comprising: athermistor, disposed adjacent to the rechargeable battery and having aresistance which varies with a temperature of the rechargeable battery;a fuel gauge, configured to calculate a charge storage capacity of therechargeable battery and determine a temperature sensing resultaccording to the resistance of the thermistor; a charging controlcircuit, configured to control how the charging circuit charges therechargeable battery and determine the temperature sensing resultaccording to the resistance of the thermistor; and a switch module,coupled between the processor, the thermistor, the fuel gauge and thecharging control circuit and configured to conduct electric currentsbetween the thermistor and a fuel gauge or between the thermistor and acharging control circuit according to a state of the processor, whereinthe fuel gauge or the charging control circuit determines thetemperature sensing result via the thermistor.
 18. The electronic systemaccording to claim 17, wherein when the processor is operated in aworking state, the switch module conducts electric currents between thethermistor and the fuel gauge, wherein the fuel gauge determines thetemperature of the rechargeable battery according to the resistance ofthe thermistor and thereby determines the temperature sensing result.19. The electronic system according to claim 18, wherein the fuel gaugeis further configured to transmit the temperature sensing result to theprocessor, wherein the processor controls how the charging circuitcharges the rechargeable battery according to the temperature sensingresult.
 20. The electronic system according to claim 17, wherein whenthe processor is not operated in a working state, the switch moduleconducts electric currents between the thermistor and the chargingcontrol circuit, wherein the charging control circuit determines thetemperature of the rechargeable battery according to the resistance ofthe thermistor and determines the temperature sensing result.
 21. Theelectronic system according to claim 20, wherein the charging controlcircuit is further configured to adjust how the charging circuit chargesthe rechargeable battery according to the temperature sensing result.22. The electronic system according to claim 20, wherein when theelectronic system is operated in a state selected from a sleeping state,a shutdown state and a crashed state, the processor is not operated inthe working state.
 23. The electronic system according to claim 17,wherein the switch module is further configured to determine the stateof the processor according to a state signal of the processor.
 24. Theelectronic system according to claim 17, wherein the charging controlcircuit comprises: a first resistor, electrically connected between thecharging circuit and a first voltage source; a serial resistor,electrically connected between a second voltage source and a groundingterminal and comprising a plurality of resistors connected in series,wherein resistances of the plurality of resistors respectively relatesto the resistance of the thermistor; and a plurality of comparators,wherein each comparator of the plurality of comparator comprises apositive input terminal electrically connected between two adjacentresistors of the plurality of resistors, a negative input terminalcoupled between the switch module and the first resistor, and an outputterminal coupled to the charging circuit.
 25. The electronic systemaccording to claim 17, wherein the thermistor is a negative temperaturecoefficient (NTC) thermistor or a positive temperature coefficient (PTC)thermistor.